"The arc of the moral universe is long, but it bends toward justice." According media reports, this quote keeping Obama company on his wheat-colored carpet is from King.

Except it's not a King quote. The words belong to a long-gone Bostonian champion of social progress. His roots in the republic ran so deep that his grandfather commanded the Minutemen at the Battle of Lexington.

For the record, Theodore Parker is your man, President Obama. Unless you're fascinated by antebellum American reformers, you may not know of the lyrically gifted Parker, an abolitionist, Unitarian minister and Transcendentalist thinker who foresaw the end of slavery, though he did not live to see emancipation. He died at age 49 in 1860, on the eve of the Civil War.

A century later, during the civil rights movement, King, an admirer of Parker, quoted the Bostonian's lofty prophecy during marches and speeches. Often he'd ask in a refrain, "How long? Not long." He would finish in a flourish: "Not long, because the arc of the moral universe is long, but it bends toward justice."

King made no secret of the author of this idea. As a Baptist preacher on the front lines of racial justice, he regarded Parker, a religious leader, as a kindred spirit.

Yet somehow a mistake was made and magnified in our culture to the point that a New England antebellum abolitionist's words have been enshrined in the Oval Office while attributed to a major 20th-century figure. That is a shame, because the slain civil rights leader and Nobel Peace Prize laureate was so eloquent in his own right. Obama, who is known for his rhetorical skills, is likely to feel the slight to King -- and Parker.

My investigation into this error led me to David Remnick's biography of Obama, "The Bridge," published this year. Early in the narrative, Remnick, the editor of the New Yorker, presents this as "Barack Obama's favorite quotation." It appears that neither Remnick nor Obama has traced the language to its true source.

Parker said in 1853: "I do not pretend to understand the moral universe; the arc is a long one. . . . But from what I see I am sure it bends toward justice."

The president is at minimum well-served by Parker's presence in the room. Parker embodied the early 19th-century reformer's passionate zeal for taking on several social causes at once. Many of these reformers were Unitarians or Quakers; some were Transcendentalists. Most courageously, as early as the 1830s, they opposed the laws on slavery and eventually harbored fugitives in the Underground Railroad network of safe houses. Without 30 years of a movement agitating and petitioning for slave emancipation, Lincoln could not have ended slavery with the stroke of a pen in the midst of war. Parker was in the vanguard that laid the social and intellectual groundwork.

The familiar quote from Lincoln woven into Obama's rug is "government of the people, by the people and for the people," the well-known utterance from the close of his Gettysburg Address in 1863.

Funny that in 1850, Parker wrote, "A democracy -- that is a government of all the people, by all the people, for all the people."

Theodore Parker, Oval Office wordmeister for the ages.

Jamie Stiehm, a journalist, is writing a book on the life of Lucretia Mott, a 19th-century abolitionist and women's rights leader.